JP4204758B2 - Manufacturing method of resin-coated rubber gasket - Google Patents

Description

【００２２】
表１より判るように、比較例１と比較して実施例１〜３の各ガスケットはいずれも流体との接触がなく良好である。また、ガスケット下面に溝を入れた実施例２および実施例３のガスケットは、ふっ素樹脂とゴムの境目に集中する応力を溝によって分散するという効果もある。
【００２３】
以上、本発明に関して詳細に説明したが、本発明は上記に限らず種々の変更が可能である。
例えば、下面に溝を入れたガスケットにおいて、溝の断面形状を円弧状としたが、これを他の形状に変更できることや、溝を直線状としたが、曲線状とできることも言うまでもない。
更に、プレート式熱交換器用ガスケットに限らず、その他の各種シール材、特に高温下や薬品下に晒されるようなシール材として好適に使用できる。
【００２４】
【発明の効果】
以上述べたように、本発明によれば、伝熱面のガスケットを設置する部分の一部あるいは全部に溝のない構造のプレート式熱交換器においても、ガスケットのゴムの部分が流体と接触しないため、ゴムの劣化、溶出がなく、特に食品業界で使用されるプレート式熱交換器に適したガスケットを提供することができる。
【図面の簡単な説明】
【図１】本発明によるふっ素樹脂被覆ゴムガスケットの断面図である。
【図２】本発明によるふっ素樹脂被覆ゴムガスケットの製造方法を説明するための成形型の構成図である。
【図３】本発明によるふっ素樹脂被覆ゴムガスケットの製造方法を説明するための他の成形型の構成図である。
【図４】本発明によるふっ素樹脂被覆ゴムガスケットの製造方法を説明するための他の成形型の構成図である。
【図５】本発明によるふっ素樹脂被覆ゴムガスケットの製造方法を説明するための他の成形型の構成図である。
【図６】本発明によるふっ素樹脂被覆ゴムガスケットの他の実施例を示す断面図である。
【図７】本発明によるふっ素樹脂被覆ゴムガスケットの製造方法を説明するための他の成形型の構成図である。
【図８】本発明の他の実施例を示すふっ素樹脂被覆ゴムガスケットの断面図である。
【図９】プレート式熱交換器の一例を示す図である。
【図１０】従来のふっ素樹脂被覆ゴムガスケットの断面図である。
【図１１】従来のふっ素樹脂被覆ゴムガスケットを溝に入れて使用した場合の流体との接触を示す断面図である。
【図１２】従来のふっ素樹脂被覆ゴムガスケットを溝に入れないで使用した場合の流体との接触を示す断面図である。
【符号の説明】
１ 伝熱プレート
２ 伝熱面
３ 流体の通路
４ 溝
５ ガスケット
６ ふっ素樹脂シート
６’ 中芯ゴムの下面の一部を被覆する被覆部
６ａ ふっ素樹脂シート
７ 中芯ゴム
７ａ ゴム組成物からなる棒状体
８ 成形型（上型）
９ 成形型（下型）
１０ 被覆型
１１ 半円柱
１２ 流体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to gaskets used to prevent fluid leakage in a wide range of fields such as piping and equipment, particularly plate-type heat exchange used for heat exchange between fluids in the food industry and chemical industry. The present invention relates to an improvement in a device gasket and a method for manufacturing the same.
[0002]
[Prior art]
In general, a plate heat exchanger is composed of a plurality of rectangular heat transfer plates 1 having holes serving as fluid passages 3 at four corners of a heat transfer surface 2 through gaskets 5 as shown in FIG. It has a laminated structure, and by changing the shape of the gasket 5, two types of fluids are alternately passed through the heat transfer surface 2 on the heat transfer plate 1, and heat exchange is performed via the heat transfer plate 1. Widely used in the food and chemical industries.
The gasket 5 used in this plate heat exchanger is attached to the groove 4 on the outer periphery of the heat transfer plate 1 and plays an important role for sealing between two kinds of fluids and between the fluid and the outside. An elongated rubber molded product having a polygonal cross section is often used.
[0003]
Further, the gasket 5 is generally one in which a rubber compound mainly composed of rubber and carbon black is cross-linked, and the types of rubber used are ethylene propylene rubber (EPM and EPDM), acrylonitrile butadiene rubber (NBR). Hydrogenated acrylonitrile butadiene rubber (HNBR), fluorine rubber (FKM), and the like are selectively used depending on the type and temperature of the fluid.
[0004]
Among these, since the food industry has been mainly sterilized at high temperatures for a short time, the temperature of the internal fluid often rises to about 150 ° C, and acids etc. are used to clean the heat exchanger. In some cases, chemicals for cleaning are used as fluids. In the gasket 5 in which the rubber compound is cross-linked as described above, carbon black is detached due to deterioration of the rubber, and elution of components in the rubber is seen. It can be a problem.
Therefore, in recent years, gaskets coated with a fluorine resin that has high heat resistance and chemical resistance and does not cause deterioration or elution have come to be used. A linear core rubber 7 made of a rubber composition mainly composed of a reinforcing filler and a resin sheet 6 covering the surface of the core rubber is integrated with a resin. A rubber gasket has been proposed (Japanese Patent Application No. 11-240203).
[0005]
[Problems to be solved by the invention]
However, the resin-coated rubber gasket as described above is used by being mounted in a groove corresponding to the shape of the gasket, as shown in FIG. 11, and the portion in contact with the fluid 12 is limited to the upper surface and the upper side surface. It was.
[0006]
On the other hand, depending on the type of plate heat exchanger, there is a structure in which there is no groove in a part or all of the part where the gasket of the heat transfer surface is installed. As shown in FIG. 12, the rubber part on the lower side and the lower side of the gasket side surface comes into contact with the fluid, and the components in the rubber may be eluted.
[0007]
The present invention has been made to solve the above problems, and maintains a predetermined tensile strength, elongation, and compression set value even when used at high temperatures and under chemicals. It is an object of the present invention to provide a gasket that is free from eluate and that is suitable for a plate heat exchanger used in the food industry regardless of the shape of the groove of the plate.
[0008]
[Means for Solving the Problems]
Between the upper mold and the lower mold provided with the cavity, a resin sheet on which a rubber composition mainly composed of uncrosslinked rubber and a reinforcing filler is placed, and the upper mold and the lower mold are pressed. In the method for manufacturing a rubber gasket, the lower mold is provided with a lid so as to cover a part of the opening surface of the cavity, and the upper mold is provided with an upper surface of the lid via a resin sheet after pressing. In addition , the resin sheet is rotated to a part of the lower surface in addition to the upper surface and the side surface of the rubber composition by providing a recess that contacts the side surface and pressing the upper mold and the lower mold at the crosslinking temperature of the rubber. The gist of the present invention is a method for producing a resin-coated rubber gasket, characterized by producing a resin-coated rubber gasket .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing a resin-coated rubber gasket of the present invention (hereinafter simply referred to as “gasket”) corresponding to FIG. 10 showing a conventional gasket. 2 (a) and 2 (b) are cross-sectional views for explaining the gasket manufacturing method of the present invention.
[0010]
As shown in the figure, a gasket 5 according to the present invention covers a linear core rubber 7 made of a rubber composition mainly composed of rubber and a reinforcing filler such as carbon black, and covers the surface of the core rubber. In the resin-coated rubber gasket in which the resin sheet 6 is integrated, the resin sheet 6 has a covering portion 6 ′ that extends to the lower surface in addition to the upper and side surfaces of the rubber gasket. Note that silica can also be used as the reinforcing filler.
As shown in FIG. 2 (a), the gasket 5 is attached with a lid (here, a covering mold 10) that does not cover all the cavity opening surfaces of one mold (here, the lower mold 9). The resin sheet 6a is stretched so as to cover it, and an adhesive is applied onto the resin sheet 6a, and then a rod-shaped body 7a made of a rubber composition mainly composed of uncrosslinked rubber and carbon black is mounted. Then, as shown in FIG. 5B, the other mold (the upper mold 8 in this case) is mounted, and the molds 8 and 9 are maintained at the rubber crosslinking temperature and pressed at a predetermined pressure. By this thermoforming, the rod-like body 7a is formed into a predetermined cross-sectional shape with cross-linking, and at the same time, the resin sheet 6a is integrally joined to the surface, and the rubber portion on the lower surface in addition to the upper and side surfaces of the gasket Is covered. In addition, 6 'is a coating | coated part which coat | covers a part of rubber part of a lower surface. And the gasket 5 shown in FIG. 1 is obtained by removing the metal mold | die 8 and 9 and removing the excess resin sheet 6a.
Moreover, you may perform secondary bridge | crosslinking for this gasket 5 using oven as needed.
[0011]
In the above, the type of the covering mold 10 is not particularly limited. For example, in order to improve the removal property from the mold, as shown in FIG. As shown, a part in which the covering die 10 is incorporated in a part of the lower die 9 can be cited.
[0012]
In the above, the resin sheet includes a fluororesin sheet, and the kind thereof is not particularly limited. For example, polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) ), Tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), and the like. it can.
As a resin to be used, any resin material such as general-purpose plastics such as polyethylene and polypropylene can be applied in addition to the fluorine resin.
Regarding the thickness, a sheet in the range of 0.01 mm to 0.5 mm is used in consideration of chemical resistance, sealing properties, and moldability, but it is preferably 0.05 mm to 0.25 mm. This is because if the sheet is too thin, the fluororesin sheet 6a is stretched during integral molding in FIG. 2 (b), causing breakage. Conversely, if the sheet is too thick, the gasket 5 is connected to the heat transfer plate. This is because the operation of fitting into the groove becomes difficult, or the resin sheet 6 is deformed by stress relaxation and easily leaks.
[0013]
Furthermore, it is preferable to perform an appropriate surface treatment on the surface on which the rod-like body 7a of the resin sheet 6a is placed. As the treatment liquid, for example, in the case of a fluororesin sheet, a complex compound solution obtained by adding metallic sodium to a tetrahydrofuran solution of naphthalene can be used. Thereby, the adhesiveness of the fluororesin sheet | seat 6 and the center rubber | gum 7 can be improved more.
As an adhesive applied to the resin sheet 6a, for example, in the case of a fluororesin sheet, organosiloxane can be used. This adhesive need not be applied to the entire surface of the fluororesin sheet 6 a, and may be applied along the groove of the cavity of the mold 9. In the joint portion between the core rubber 7 of the gasket 5 and the fluororesin sheet 6, the joint strength is particularly weak at the bent portion of the core rubber 7, and therefore the cavity of the mold 9 corresponding to the bent portion of the core rubber 7. By applying the adhesive along the groove, it is possible to suppress peeling of the fluororesin sheet 6 at this portion.
[0014]
On the other hand, the type of the rubber composition forming the core rubber 7 is not particularly limited, and is appropriately selected according to use conditions.
For example, when used as a gasket for a plate heat exchanger, use ethylene propylene rubber (EPM, EPDM), acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), fluorine rubber (FKM), etc. However, it is also possible to use a resin that is generally used for a sealing material such as a thermoplastic elastomer, and carbon black or a crosslinking agent can be added to the resin.
[0015]
Carbon black, which is a typical reinforcing filler, can be carbon black used as a normal rubber reinforcing agent such as MT, FEF, SRF, HAF type, etc., but tensile strength, elongation, compression In order to obtain a good value for permanent distortion or the like, it is desirable to use a finer particle size than HAF.
As the cross-linking agent, those conventionally used for this type of gasket may be used. However, when applied to a plate heat exchanger in the food industry, it is preferable to use a peroxide-based cross-linking agent. . Moreover, you may use a well-known co-crosslinking agent together.
Moreover, you may mix | blend the other additive conventionally used for this kind of gasket as needed.
The composition of the rubber composition containing these is not limited and is appropriately selected according to the required physical properties.
[0016]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.
Example 1
As shown in FIG. 2A, a lid (covering die) 10 is attached to a molding die (lower die) 9 so that the opening surfaces of the cavities are not completely hidden, and PTFE resin is 1500 mm × 500 mm in thickness 0. .Positioning pin holes are made in a fluororesin sheet 6a which is surface-treated with a complex compound solution obtained by forming metal sheet into a 2mm sheet and adding metal sodium to a solution of naphthalene in tetrahydrofuran. It is stretched so as to cover a part of the cavity opening surface of the molding die (lower die) 9 to which the covering die 10 is attached so as to face the die (upper die) 8, and the surface of the fluororesin sheet 6a. After applying adhesive (organosiloxane) along the groove shape of the cavity on the treated surface, uncrosslinked rubber assembly consisting of EPDM rubber, peroxide-based crosslinking agent (dicumyl peroxide), and carbon black A rod-like body 7a formed by extruding an object into a rod-like shape is placed, and then pressed with an upper die 8 and heated at 170 ° C. for 20 minutes as shown in FIG. The gasket was taken out, excess burr portions were cut off, and then secondary crosslinking was performed in an oven at 170 ° C. for 2 hours to produce a gasket 5 whose cross section was shown in FIG.
[0017]
(Example 2)
As shown in FIG. 5, Example 1 and Example 1 were used except that a covering mold 10 having a semi-cylindrical convex portion 11 having a radius of 0.8 mm for attaching a groove for dispersing stress to the PTFE covering portion on the lower surface was used. Similarly, a gasket 5 having a cross section shown in FIG. 6 was produced. In addition, 6 'is a coating | coated part which coat | covers a part of lower surface rubber part.
[0018]
(Example 3)
As shown in FIG. 7, the embodiment was carried out except that a molding die (upper die) 8 was provided with a semi-cylindrical convex portion 11 having a radius of 0.8 mm for attaching a groove for dispersing stress to the rubber portion on the lower surface. A gasket 5 having a cross section as shown in FIG.
[0019]
(Comparative Example 1)
A gasket 5 having a cross section as shown in FIG. 10 was prepared in the same manner as in Example 1 except that the covering mold was not used.
[0020]
Table 1 shows the results of a test in which the gaskets of Examples 1 to 3 and Comparative Example 1 were set on a plate without a groove and it was confirmed whether the bottom surface rubber portion was in contact with the fluid.
[0021]
[Table 1]

[0022]
As can be seen from Table 1, compared to Comparative Example 1, each of the gaskets of Examples 1 to 3 is good because there is no contact with the fluid. Further, the gaskets of Example 2 and Example 3 in which grooves are formed on the lower surface of the gasket also have an effect of dispersing stress concentrated on the boundary between the fluororesin and the rubber by the grooves.
[0023]
Although the present invention has been described in detail above, the present invention is not limited to the above, and various modifications can be made.
For example, in the gasket having a groove on the lower surface, the cross-sectional shape of the groove is an arc shape, but it can be changed to another shape, or the groove is a straight line, but it is needless to say that it can be a curved shape.
Furthermore, it is not limited to the plate heat exchanger gasket, but can be suitably used as other various sealing materials, particularly as a sealing material that is exposed to high temperatures or chemicals.
[0024]
【The invention's effect】
As described above, according to the present invention, the rubber portion of the gasket does not come into contact with the fluid even in the plate type heat exchanger having a groove-free structure in part or all of the portion where the gasket of the heat transfer surface is installed. Therefore, there is no deterioration or elution of rubber, and a gasket suitable for a plate heat exchanger used particularly in the food industry can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fluororesin-coated rubber gasket according to the present invention.
FIG. 2 is a block diagram of a mold for explaining a method for producing a fluororesin-coated rubber gasket according to the present invention.
FIG. 3 is a configuration diagram of another mold for explaining a method for producing a fluororesin-coated rubber gasket according to the present invention.
FIG. 4 is a configuration diagram of another mold for explaining a method for producing a fluororesin-coated rubber gasket according to the present invention.
FIG. 5 is a configuration diagram of another mold for explaining a method for producing a fluororesin-coated rubber gasket according to the present invention.
FIG. 6 is a cross-sectional view showing another embodiment of a fluororesin-coated rubber gasket according to the present invention.
FIG. 7 is a configuration diagram of another mold for explaining a method for producing a fluororesin-coated rubber gasket according to the present invention.
FIG. 8 is a cross-sectional view of a fluororesin-coated rubber gasket showing another embodiment of the present invention.
FIG. 9 is a view showing an example of a plate heat exchanger.
FIG. 10 is a cross-sectional view of a conventional fluororesin-coated rubber gasket.
FIG. 11 is a cross-sectional view showing contact with a fluid when a conventional fluororesin-coated rubber gasket is used in a groove.
FIG. 12 is a cross-sectional view showing contact with a fluid when a conventional fluororesin-coated rubber gasket is used without being inserted into a groove.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat transfer plate 2 Heat transfer surface 3 Fluid path 4 Groove 5 Gasket 6 Fluororesin sheet 6 'Covering part 6a covering part of the lower surface of the core rubber Fluororesin sheet 7 Core rubber 7a Bar shape made of rubber composition Body 8 Mold (Upper mold)
9 Mold (Lower mold)
10 Coating type 11 Semi-cylinder 12 Fluid

Claims (1)

Between the upper mold and the lower mold provided with the cavity, a resin sheet on which a rubber composition mainly composed of uncrosslinked rubber and a reinforcing filler is placed, and the upper mold and the lower mold are pressed. In the method for manufacturing a rubber gasket, the lower mold is provided with a lid so as to cover a part of the opening surface of the cavity, and the upper mold is provided with an upper surface of the lid via a resin sheet after pressing. and a recess such that contact with the side surface, by pressing the upper mold and said lower mold at a crosslinking temperature of the rubber, the upper surface of the resin sheet is a rubber composition, around up to the part of the lower surface in addition to side A method for producing a resin-coated rubber gasket, comprising producing a resin-coated rubber gasket .

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